By DJ Short




There are several important points to consider when choosing the optimum time to harvest your marijuana crop. There are different factors to consider between indoor and outdoor marijuana plants. There is the difference between Sativas and Indicas in bloom duration and final effect.

There is the difference between early and late harvest to encourage head to body high respectively. There is the issue of chemistry because what we are really considering in terms of the ripeness relates directly to the chemical nature and state of the plant at harvest. Last, but not least, is the concept of the window for marijuana harvest, where I will begin.



Window For Harvesting Your Marijuana Crop

This term indicates the period during which the plant is at its optimum state of ripeness. The window opens when the plant is first ripe. Somewhere along the line the plant becomes over-ripe which signifies the closing of the window of harvest.

For most Indicas grown indoors, the window of harvest is about two weeks long give or take a couple of days for various strains. Indoors, if going directly from an 18/6 hour vegetative light cycle to a 12/12 hour bud cycle, most indicas take about eight weeks to fully mature.

As to outdoors I can only speak from experience at the 45th parallel and the bloom times there. At the 45th parallel I've found most Indicas to be at peak harvest starting at the beginning of October, sometimes very late September, and running until the end of October, sometimes running into November during mild years or in a greenhouse. My favorite time to harvest a nice Blueberry Indica outdoors is in the second to third week of October.

For Sativa grown either indoors or outdoors, the window may be open much longer. Some Sativas take up to thirteen weeks to mature indoors. Outdoors many will go well into November and even December, if conditions are right (again, this is near or at the 45th parallel). Head High or Body Stone?

An important consideration has to do with one's preference for a head high or more of a body high. A good head high can positively influence one's mental state much like a psychedelic; whereas a good body high is more similar to a narcotic effect. Generally, head highs tend to be more up and body highs tend to be more down. Suffice it to say that a good healthy mix of the two is a fine goal to achieve.

Sativas and early window harvests tend to be more of a head high, whereas Indicas and late window harvests tend to be more of a body high. Given this rule of thumb you can pretty much come up with what you want. That is, if you prefer a very psychedelic head high, then an early harvested Sativa might do best.

If a very narcotic body high is desired, then a late harvest indicas would probably do best. For that best-of-both worlds high, experimentation with late harvested sativas and early-to-mid harvested indicas usually proves interesting.



Magnify Your Buds

When we speak of various highs experienced by different products, we are noting variations in plant chemistry. The chemicals we enjoy are produced within the glandular stalked trichomes, along the surfaces of the bud flowers (calyxes), bracts, leaves and stems, starting in or around the fourth week of the bud cycle. More and more of these trichomes develop as the plant matures.

I highly recommend that the serious cannabis student acquire a 30X power, illuminated magnifier. These can be found at most local electronics stores, often for under fifteen dollars. With the aid of the magnifier one can learn more about the detail of trichome development and ripeness.

As far as trichomes are concerned, the tall ones with swollen, clear, bulbous heads are what to shoot for. The denser the concentration, the greater the potency.




The Cycle Of Marijuana Plant Maturity

Starting in the third or fourth week of the flowering light cycle, glandular stalked trichomes will begin to form along the surfaces of leaves, flowers, bracts and stems. At the same time, more and more flowers (also called calyxes) develop into densely-packed floral clusters.

The pistils of the young flowers are bright white and turn reddish brown with age. The pistils and flowers develop from the bottom of the bud to the top. The older, lower pistils are the first to turn reddish brown. For most basic indicas this usually happens by the sixth week in the flowering cycle. It is about this time that the calyxes begin to swell.

Calyx swelling is a major indicator of peak maturity. The lowest, oldest calyxes swell first and the swelling works its way up to the highest, youngest flowers on each bud. At peak maturity about 90% of the calyxes will almost look seeded, they are so fat.

Three quarters to 90% of the pistils will have turned reddish brown as well. For a basic Indica this takes well into the seventh week of the flowering cycle.

By the end of the eighth week most of the calyxes will have swollen and a surge of trichome development has coated most of the buds. It is now that the development of a very discerning palate comes into play to determine the finest harvest time. Remember - patience is a virtue and often a discipline.

The ripening signs for most Sativas are highly similar, except extended over a longer period of time. Occasionally, some Sativas have windows of peak harvest that actually open and close. That is, for a week or so the plant may exhibit signs of peak ripeness.

However, a week later the plant may have a growth spurt, which lowers the trichome-to-fibre ratio and overall potency for a little while. Usually a fibrous growth spurt is accompanied by a corresponding trichome increase. Again, time and experience are the key elements in this regard.




Changes In Marijuana Chemistry

As the plant matures through its window of harvest its chemistry changes. As the window closes, the more desirable compounds begin breaking down into less desirable ones. Primarily it is THC breaking down in CBNs and CBDs.

Which particular combination of chemicals is the most desirable is purely a matter of taste and choice, developed over time and with experience. Set and setting also play an important role in determining which type of product is best appreciated.

Pleasant head highs are often desirable for social occasions, whereas a narcotic late-window Indica may work better as an evening medicinal herb. The main point is that these differences are chemical in nature and more research is needed to more fully understand this phenomenon.

Another important point is that much can be done to further enhance the chemical process, especially in regard to bouquet, aroma and flavour, given the proper curing process.




More info
From Overgrow's FAQ'S

When to harvest your trichomes
There are several schools of thought as to when it is the time to harvest. I shall attempt to explain how you can determine the harvesting time that will produce the most favorable psychoactive effect for your individual preferences.

We are most concerned with the capitate-stalked trichomes, as these contain the overwhelming majority of the psychoactive cannabinoids (THC, THCV, CBN). Different cannabinoids affect the high in a multifaceted manner.


THC:
delta-9-tetrahydrocannabinol & delta-8-tetrahydrocannabinol - THC mimics the action of anandamide, a neurotransmitter produced naturally in the body, which binds with the cannabinoid receptors in the brain to produce the ‘high’ associated with marijuana. THC possesses high UV-B (280-315 nm) absorption properties.

THCV:
tetrahydrocannabivarin - prevalent in certain South African and Southeast Asian strains of cannabis. It is said to produce a ‘clearer high’ & seems to possess many of the therapeutic properties of THC.

CBD:
cannabidiol - previously believed to be psychoactive, or to contribute to the high by interacting with other cannabinoids, conversely the most recent research indicates that CBD has negligible effect on the high, it is however a strong anti-inflammatory, and may take the edge off some THC effects, such as anxiety. CBD as a non-psychoactive cannabinoid appears to be helpful for many medical conditions. CBD biosynthesizes into cannabinol (CBN) & tetrahydrocannabinol (THC).

CBN:
cannabinol - a degradation product of THC, produces a depressant effect, ‘fuzzy’ forehead.

CBC:
cannabichromene - non-psychoactive , a precursor to THC.

CBG:
cannabigerol - non-psychoactive, hemp strains often posses elevated levels of CBG while possessing only trace amounts of THC.

Heavy trichome production is not necessarily an indication of a potent plant. Some hemp strains have moderate layers of trichomes yet pack only a strong headache. In a drug strain, a thick layer of trichomes is a symbol that it may well posses an elevated potency level, but it is certainly not a guarantee.

What defines a cannabis drug strain is the plant's ability to produce THC & THCV.

A small 25x or stronger pocket microscope, which can be picked up inexpensively at an electronics store like Radio Shack, works well for getting a closer peek at your trichome development. We are examining are the capitate stalked glandular trichomes, the coloration of these gland heads can vary between strains and maturity. Most strains start with clear or slightly amber heads which gradually become cloudy or opaque when THC levels have peaked and are beginning to degrade. Regardless of the initial color of the secretory cavity, with careful observation you should be able to see a change in coloration as maturity levels off.

Some cultivators wait for about half of the secretory cavities to go opaque before harvesting, to ensure maximum THC levels in the finished product. Of course nothing tells the truth more than your own perception, so try samples at various stages to see what is best for you & the phenotype your are growing. While you may be increasing the total THC level in the bud by allowing half of the glands to go opaque, the bud will also have a larger percentage of THC breakdown products such as CBN, which is why some people choose to harvest earlier while most of the secretory cavities are still clear.

Indica varieties will usually have a 10-15 day harvest window to work with. Sativas and Indica/Sativa hybrids often have an extended period to work with.


An example of times to harvest by trichome colour



Although cannabis resin glands called trichomes are structurally diverse, they come in three basic varieties:


The figures above denote capitate-stalked trichomes with green arrows, the bulbous trichomes with yellow arrows & the red arrows mark the capitate-sessile trichomes.
Bulbous:
The bulbous type is the smallest (15-30 micron). From one to four cells make up the "foot" and "stalk," and one to four cells make up the "head" of the gland. Head cells secrete a resin - presumably cannabinoids, and related compounds which accumulate between the head cells and the cuticle. When the gland matures, a nipple-like protrusion may form on the membrane from the pressure of the accumulating resin. The bulbous glands are found scattered about the surfaces of the above-ground plant parts.

Capitate-Sessile:
The second type of gland is much larger & is more numerous than the bulbous glands. They are called capitate, which means having a globular-shaped head. On immature plants, the heads lie flush, appearing not to have a stalk and are called capitate sessile. They actually have a stalk that is one cell high, although it may not be visible beneath the globular head. The head is composed of usually eight, but up to 16 cells, that form a convex rosette. These cells secrete cannabinoids, and related compounds which accumulate between the rosette and it's outer membrane. This gives it a spherical shape. The gland measures from 25 to 100 micron across.

Capitate-Stalked:
Cannabinoids are most abundant in the capitate-stalked gland which consists of a tier of secretory disc cells subtending a large non-cellular secretory cavity. During flowering the capitate glands that appear on the newly formed plant parts take on a third form. Some of the glands are raised to a height of 150 to 500 micron when their stalks elongate. These capitate-stalked glands appear during flowering and form their densest cover on the female flower bracts. They are also highly concentrated on the small leaves that accompany the flowers. The male flowers have stalked glands on the sepals, but they are smaller and less concentrated than on the female bracts. Male flowers form a row of very large capitate glands along the opposite sides of anthers.





Disc cells, attached to leaf or bract by stipe cells (RED) & basal cells (GREEN), release fibrillar wall matrix into secretory cavity where it contributes to thickening of subcuticular wall during enlargement of secretory cavity. Plastids (ORANGE) in disc cells produce secretions called lipoplasts which synthesize quantities of lipophilic substances that accumulate outside the plasma membrane, migrating into the endoplasmic reticular cytoplasm and through the plasma membrane and cell wall into the secretory cavity where they form vesicles (BLUE) in the secretory cavity. Vesicles in contact with the subcuticular wall release contents that contribute to the growth of the cuticle during the enlargement of the secretory cavity. THC occurs in the walls, fibrillar matrix & other contents surrounding the vesicles, but not in the vesicles. Trace amounts of THC is present in the disc cells